1. Technical Field
The present disclosure relates to a vehicle presence notification apparatus for notifying the presence of a vehicle to an outside of the vehicle by using notification sound. In particular, the present disclosure relates to notification of the presence of such a vehicle as an electric vehicle, a fuel cell vehicle, a hybrid vehicle and the like, each of which is capable of traveling with an electric motor generating rotative power from electric power.
2. Description of Related Art
A vehicle presence notification apparatus, which notifies the presence of a vehicle to the surroundings of the vehicle by using notification sound, needs to generate the notification sound that is easily-perceivable to human ears. In this relation, it is conceivable that the sound with “high frequencies” is generated as easily-perceivable notification sound. The sound with “high frequencies” is easily perceivable but is “annoying or sticking sound”, which provides an unconformable feeling to people. For example, the sound with 4 kHz is easily-perceivable but really annoying. If a vehicle travels while radiating sound with 4 kHz, the vehicle provides uncomfortable feeling to people around the vehicle.
If frequency of the notification sound is lowered for reduction of the uncomfortable feeling, the notification sound easily blends into environment noise, becomes less perceivable by humans, and becomes less effective in notification of the presence of a vehicle to the surroundings.
JP-H06-162351A describes a technique to automatically adjust sound pressure level of the notification sound to surrounding noise in order to reduce the uncomfortable feeling caused by too large of a notification sound. However, the technique disclosed in JP-H06-162351A cannot solve a difficulty of providing the high frequency notification sound and the uncomfortable feeling to people.